The purpose of the study was to investigate the effect of different kicking modality, i.e., erratic-dynamic target (EDT) versus static target (ST) on the performance of the roundhouse kick in two groups of taekwondo athletes of different skill level. Three-dimensional analysis and surface electromyography (SEMG) analysis were performed on 12 (Group A: six sub-elite, Group B: six elite) athletes to investigate muscle co-activation pattern under two conditions, i.e., EDT versus ST. In the results, the muscle recruitment ratio of the agonistic muscles was higher for Group A, whereas Group B had higher recruitment ratio for antagonist muscles. Overall, the co-activation index (CI) of hip joints appeared higher in the extensors for Group A, whereas higher CI was observed in flexor muscles for Group B with comparatively higher CI during EDT condition than ST condition. Higher value of CI was observed in flexor muscles of the knee joints among Group A during EDT conditions, in contrast, higher CI in the extensor muscles was observed among Group B during ST conditions. In conclusion, the study confirmed that erratic-dynamic movements of target could change the movement coordination pattern to maintain the joint stability of participants.

Complex structures present in a human body has relatively large degrees-of-freedom (DOFs) as compared to the requirement of a particular task. This phenomenon called motor redundancy initially deemed as a computational problem rather can be understood as having the flexibility to perform the certain task successfully. Hence, the purpose of our study was to examine the positive impact of extra DOFs (redundant DOFs) during force production tasks. For this purpose, an experimental setup was designed to simulate archery-like shooting, and purposeful organization of a redundant set of finger forces determined the stability of important performance variables as well as accurate and precise performance. DOFs were adjusted by changing the number of fingers explicitly involved in the task. The concept of motor synergy and computational framework of uncontrolled manifold (UCM) approach was used to quantify stability indices during finger force production. As a result, accuracy and precision of the task improved with an increase in DOFs. Also, the stability indices of net finger forces and moment increased with active DOFs of fingers. We concluded that the controller actively utilizes extra DOFs to increase the stability of the performance, which is associated with the improved accuracy and precision of the task.

The purpose of the study was to analyze and quantify the ability of the goalkeeper while defending shots from left and right sides of penalty area or the goal area, which frequently occurs in an actual game situation. In other words, the study aimed at verifying the reaction ability of the goalkeeper to defend goals in two different defense positions across a 3 m width area without performing dives. Eleven male goalkeepers from a university soccer league participated in the study. The goalkeepers were assigned to react to a specific target point, i.e. high, middle, low, left and right in response to the LED signal positioned at the front. Three-dimensional motion analysis system was used to perform kinematical analysis through which variables such as the approach time of reaching specific target points and the movement used to cover the defensive area were observed. In results, no significant differences were observed in approach time of the hand to the target point in both defense positions, i.e. Type-A (defense posture of positioning the hand at knee height) and Type-B (defense posture of positioning the hand at waist height). But Type-B defense position average velocity was observed faster than Type-A for blocking shots of low-middle heights. Hence, the results obtained from the study showed a possibility that being prepared in Type-A defense position will be more accurate and stable. Moreover, goalkeepers were able to occupy wider defense range in Type-A defense position than Type-B within the time period of 0.7 $ 0.8 s after triggering of the LED signal. In conclusion, the results obtained from the study pointed out that Type-A defense position can be much more effective in soccer for blocking shots from the left and right sides of the penalty area. The defense posture of positioning the hand at low height is considered more effective when defending a ball shot from areas near the penalty area than the high hand position. It was also confirmed that the available defense area can be defended widely and effectively by moving the center of the body. Further studies need to be performed to consider the cognitive perspective by applying various methods.

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